Practices at home and abroad demonstrate that coal seam water injection is an effective method of actively lowering impact tendency of work face coal seam and reducing generation of powder dusts. According to the method, high pressure water is pre-injected into a coal mass so that the coal rock mass expands its original fissure, generates new fissures, destroys the entirety of the coal rock mass, lowers its strength and releases pressure of the coal mass by use of fracturing, washing and wedging actions of the pressurized water on a weak face and physical and chemical actions of water on the coal mass. In this way, the occurrences of coal bumps are effectively avoided. The water injected into the coal mass is penetrated toward a coal block divided by the coal fissure along the fissure and stored in the fissures and pores to increase moisture of the coal mass and wet raw coal dusts in the coal mass, thereby disabling the dusts to fly and reduce an ability to generate floating dusts during coal mining.
Since a long time ago, the cognition of people for water injection in coal seam always stays in a qualitative cognition stage. However, in a traditional water injection manner, a borehole is directly sealed before water injection. This water injection manner features less water injection amount of single borehole, complex borehole sealing technique, and poor penetration effect of water in the coal seam. Thus, the water injection in the coal seam is affected. A size of a coal seam porosity is an important index representing water injection difficulty. Coal seam fissure and pore development degree are the first factors affecting the difficulty of coal seam water injection. However, because different mines enter a deep mining stage one by another in China, prominent problems of high initial stress of coal rock, undeveloped fissures and pores, low permeability, and high gas content and so on hold back the development of coal seam water injection technology. The coal seams of many mines in China are coal seams with high ground pressure and low porosity, joint fissures of coal seams are undeveloped and hard, water is difficult to inject into coal seams, and therefore a desired disaster prevention and control effect cannot be achieved. Further along with increase of mining depths of the coal mines in China, the problem of difficulty of water injection is further highlighted, which severely restricts the application of the coal seam water injection technology in deep high ground pressure coal seams of China, and hinders its prevention and control effect on the hazards of coal bumps and high concentration powder dusts. Therefore, the prior art is to be further improved and developed.